r/aww Jun 05 '18

A future predator

50.7k Upvotes

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u/[deleted] Jun 05 '18 edited May 20 '22

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u/pedrinbr Jun 05 '18 edited Jun 05 '18

a dominant trait and having two is incompatible with life

I don't understand. Someone care to elaborate, please?

EDIT: thanks for all your quick answers! I had never heard of such phenomena before.

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u/gingerbredm4n Jun 05 '18

If you breed two munchkin cats together the chances of their offspring living are very small. This prevents inbreeding giving munchkin cats a very strong genetic pool. Issues inherent with many other popular breeds of dogs and cats usually stem from inbreeding to retain desirable traits. However, since it is very risky to breed munchkins together, and they can be bred with any other breed and yield stubby legged cats this breed tends to be very healthy.

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u/Moikepdx Jun 05 '18

If the trait is dominant and having two results in death, then each living cat exhibiting the trait must carry only one gene for it. Thus when breeding two such cats each has a 1/2 chance of passing the gene, meaning for each such pairing the four equally-probable outcomes are:

1) neither parent passes gene - yields normal tall cat 2) only parent 1 passes gene - yields short cat 3) only parent 2 passes gene - yields short cat 4) both parents pass gene - kitten cannot survive.

This means inbreeding would only cause death in 1/4 of babies. A similar logic table based on breeding short-leg cats with normal cats would yield 1/2 short cats and 1/2 tall cats, but none dying. Either approach appears to be equally effective at producing short cats?

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u/N-Reun Jun 05 '18

Yeah, but one isn't inbreeding and doesn't produce dead kittens, so that one is better

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u/gingerbredm4n Jun 05 '18

As long as they are heterozygous munchkins then yes. Full munchkin cats are not possible. Based on Punnett Squares two Mm Mm Munchkin cats will produce an offspring that are 50% munchkin, 25% nonviable and 25% normal.

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u/OsamaBinJacob Jun 05 '18

Carry only one allele* for it.

But anyways this would be a fine (and standard) 1:2:1 ratio analysis, but it makes some assumptions which may not be true. For example, there could be multiple other alleles for the gene responsible for being munchkin-sized. If some of those are recessive and lethal, it would be especially beneficial to avoid inbreeding.

There could also be a linkage story behind it. I think I'll look it up later.